feat(check): add --no-merge option to reject merge commits

README.md

@@ -280,6 +280,7 @@ jobs:
   and `squash!` commits.
 - if `no_revert_sha1` is not empty, no validation is done on revert
   commits.
+- if `no_merge` is not empty, merge commits are rejected (fail instead of skip).
 - `jira_in_header` jira reference can be put in the commit header.
 - `header_length` allow to override the max length of the header line.
 - `jira_types` takes a space separated list `"feat fix"` as a parameter to override the default types requiring a jira
@@ -314,6 +315,7 @@ Then run `pre-commit install --hook-type commit-msg` to install the
 - if `allow-temp` is set, no validation is done on `fixup!` and `squash!`
   commits.
 - if `no-revert-sha1` is set, no validation is done on revert commits.
+- if `--no-merge` is set, merge commits are rejected (fail instead of skip).
 - if `--jira-in-header` jira reference can be put in the commit header.
 - `--header-length` allow to override the max length of the header line.
 - `--body-length` allow to override the max length of body lines.

action.yml

@@ -28,6 +28,9 @@ inputs:
   jira_in_header:
     description: 'If not empty, allow for jira ref in header'
     required: false
+  no_merge:
+    description: 'If not empty, merge commits are rejected.'
+    required: false
 runs:
   using: "composite"
   steps:
@@ -51,4 +54,5 @@ runs:
         GLOBAL_MAX_LENGTH: ${{ inputs.header_length }}
         GLOBAL_BODY_MAX_LENGTH: ${{ inputs.body_length }}
         GLOBAL_JIRA_IN_HEADER: ${{ inputs.jira_in_header }}
+        COMMIT_VALIDATOR_NO_MERGE: ${{ inputs.no_merge }}
       shell: bash

check.bats

@@ -32,3 +32,21 @@ teardown() {
   run env COMMIT_VALIDATOR_NO_JIRA=1 bash -c "cd '$REPO' && bash '$SCRIPT' '$BASE..$BASE'"
   [ "$status" -eq 0 ]
 }
+
+@test "check: skips merge commits by default" {
+  git -C "$REPO" checkout -q -b feature
+  git -C "$REPO" commit --allow-empty -q -m "feat(widget): add widget"
+  git -C "$REPO" checkout -q master 2>/dev/null || git -C "$REPO" checkout -q main 2>/dev/null || git -C "$REPO" checkout -q -
+  git -C "$REPO" merge --no-ff -q --no-edit feature
+  run env COMMIT_VALIDATOR_NO_JIRA=1 bash -c "cd '$REPO' && bash '$SCRIPT' '$BASE..HEAD'"
+  [ "$status" -eq 0 ]
+}
+
+@test "check: --no-merge rejects merge commits in range" {
+  git -C "$REPO" checkout -q -b feature
+  git -C "$REPO" commit --allow-empty -q -m "feat(widget): add widget"
+  git -C "$REPO" checkout -q master 2>/dev/null || git -C "$REPO" checkout -q main 2>/dev/null || git -C "$REPO" checkout -q -
+  git -C "$REPO" merge --no-ff -q --no-edit feature
+  run env COMMIT_VALIDATOR_NO_JIRA=1 COMMIT_VALIDATOR_NO_MERGE=1 bash -c "cd '$REPO' && bash '$SCRIPT' '$BASE..HEAD'"
+  [ "$status" -ne 0 ]
+}

check.sh

@@ -5,12 +5,22 @@ set -eu
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
 source $DIR/validator.sh
 
-git log --no-merges --pretty="%H" --no-decorate $1 |
+NO_MERGES_FLAG="--no-merges"
+if [[ -n "${COMMIT_VALIDATOR_NO_MERGE:-}" ]]; then
+  NO_MERGES_FLAG=""
+fi
+
+git log $NO_MERGES_FLAG --pretty="%H" --no-decorate $1 |
 while IFS= read -r COMMIT
 do
-   MESSAGE=`git log -1 --pretty='%B' $COMMIT`
-   echo "checking commit ${COMMIT}..."
-   validate "$MESSAGE"
+  MESSAGE=`git log -1 --pretty='%B' $COMMIT`
+  echo "checking commit ${COMMIT}..."
+  FIRST_WORD=$(echo "${MESSAGE%% *}" | tr '[:upper:]' '[:lower:]')
+  if [[ "${FIRST_WORD}" == merge ]]; then
+    echo "error: merge commits are not allowed"
+    exit 1
+  fi
+  validate "$MESSAGE"
 done
 
 echo "All commits successfully checked"

check_message.bats

@@ -39,6 +39,24 @@ teardown() {
   [ "$status" -eq 0 ]
 }
 
+@test "check_message: --no-merge rejects MERGE_MSG path" {
+  echo "Merge branch 'foo' into 'bar'" > "$TMPFILE"
+  run bash "$SCRIPT" --no-merge "/some/path/MERGE_MSG"
+  [ "$status" -ne 0 ]
+}
+
+@test "check_message: --no-merge rejects message starting with 'Merge'" {
+  echo "Merge branch 'foo' into 'bar'" > "$TMPFILE"
+  run bash "$SCRIPT" --no-merge "$TMPFILE"
+  [ "$status" -ne 0 ]
+}
+
+@test "check_message: --no-merge still accepts valid commit" {
+  echo "feat(widget): add a wonderful widget" > "$TMPFILE"
+  run bash "$SCRIPT" --no-merge --no-jira "$TMPFILE"
+  [ "$status" -eq 0 ]
+}
+
 @test "check_message: strips comment lines before validating" {
   printf "# This is a comment\nfeat(scope): valid subject\n" > "$TMPFILE"
   run bash "$SCRIPT" --no-jira "$TMPFILE"

check_message.sh

@@ -2,13 +2,14 @@
 
 set -eu
 
-unset COMMIT_VALIDATOR_ALLOW_TEMP COMMIT_VALIDATOR_NO_JIRA COMMIT_VALIDATOR_NO_REVERT_SHA1 GLOBAL_JIRA_IN_HEADER GLOBAL_MAX_LENGTH GLOBAL_BODY_MAX_LENGTH GLOBAL_JIRA_TYPES
+unset COMMIT_VALIDATOR_ALLOW_TEMP COMMIT_VALIDATOR_NO_JIRA COMMIT_VALIDATOR_NO_REVERT_SHA1 COMMIT_VALIDATOR_NO_MERGE GLOBAL_JIRA_IN_HEADER GLOBAL_MAX_LENGTH GLOBAL_BODY_MAX_LENGTH GLOBAL_JIRA_TYPES
 
 while [[ $# -gt 0 ]]; do
   case "$1" in
     --no-jira ) COMMIT_VALIDATOR_NO_JIRA=1; shift ;;
     --allow-temp ) COMMIT_VALIDATOR_ALLOW_TEMP=1; shift ;;
     --no-revert-sha1 ) COMMIT_VALIDATOR_NO_REVERT_SHA1=1; shift ;;
+    --no-merge ) COMMIT_VALIDATOR_NO_MERGE=1; shift ;;
     --jira-in-header ) GLOBAL_JIRA_IN_HEADER=1; shift ;;
     --header-length=* ) GLOBAL_MAX_LENGTH="${1#*=}"; shift ;;
     --header-length ) GLOBAL_MAX_LENGTH="$2"; shift 2 ;;
@@ -28,6 +29,10 @@ source "$DIR/validator.sh"
 
 if [[ "$1" == *MERGE_MSG ]]
 then
+  if [[ -n "${COMMIT_VALIDATOR_NO_MERGE:-}" ]]; then
+    echo "error: merge commits are not allowed"
+    exit 1
+  fi
   # ignore merge message (merge with --no-ff without conflict)
   exit
 fi
@@ -38,9 +43,12 @@ MESSAGE=$(sed '/^#/d' "$1")
 FIRST_WORD=$(echo "${MESSAGE%% *}" | tr '[:upper:]' '[:lower:]')
 if [[ "${FIRST_WORD}" == merge ]]
 then
-   # ignore merge commits (merge after conflict resolution)
+  if [[ -n "${COMMIT_VALIDATOR_NO_MERGE:-}" ]]; then
+    echo "error: merge commits are not allowed"
+    exit 1
+  fi
+  # ignore merge commits (merge after conflict resolution)
   exit
-
 fi
 
 # print message so you don't lose it in case of errors